Head suspension assembly mounting nonvolatile memory and magnetic disk device

ABSTRACT

A head suspension assembly  4  having an arm  17  supported so as to rotate, an elastically flexible suspension  16  of which one end is fixed to an end of the arm and other end mounts a magnetic head  2,  and a signal transmission line  18  fixed on the suspension and the arm which connects the magnetic head with a main FPC, wherein a head amplifier  8  which transmits and receives signals to and from the magnetic head and a nonvolatile memory  9  which stores optimized control parameters of the magnetic head and the head amplifier are mounted together on the head suspension assembly and the head amplifier and the nonvolatile memory are electrically connected to the signal transmission line.

BACKGROUND OF THE INVENTION

[0001] This invention relates to a magnetic disk device, especially to the magnetic disk device storing control parameters specific to the magnetic disk device into a nonvolatile memory, and a head suspension assembly used in the magnetic disk device.

[0002] Generally, a magnetic disk device comprising plural magnetic disks having a magnetic layer which records data and is formed on a non-magnetic substrate and being stacked along a rotating shaft of a spindle motor, and magnetic heads for recording and reproducing data which are mounted on one end of a suspension of which the other end is fixed to an end of an arm, placed on each of the magnetic disk surfaces and positioned by the arm driven by an actuator, is known. In a hard disk device having above structure, the magnetic head is arranged so as to access to the desired position floating with height of tens of nanometers on the fast rotating magnetic disk surface in the recording and reproduction of data.

[0003] Data are recorded or reproduced to or from a track of concentric circles on the magnetic disk by the magnetic head. Generally, a sequence of operations of the magnetic disk device is controlled by MPU (Micro Processing Unit) that executes control programs based on control parameters stored in a nonvolatile memory or transferred into RAM (Random Access Memory) from the nonvolatile memory.

[0004] The magnetic disk device has various management data as follows: the device operation mode fit for each customer such as ON/OFF of a cache and the setting of master/slave, parameters to be set up for each magnetic head, such as an optimum recording current and an optimum bias current obtained from recording and reproducing characteristics of each magnetic head, physical offset position of a recording head and a reproducing head (hereafter referred to as offset position), amplifying gain of a head amplifier, and parameters to be set up for each magnetic head or data zone such as filter constants. These management data vary in every drive and rewriting is required for the change of setting up. Therefore, these data are generally stored in a semiconductor memory that is a nonvolatile rewritable memory such as EEPROM (Electrically Erasable and Programmable Read Only Memory) or FROM (Flash Read Only Memory), or in a management data area provided on a part of the magnetic disk.

[0005] According to recent downsizing and increasing storage capacity of the magnetic disk device, a high performance magnetic head is required. As the high performance magnetic head, a composite type magnetic head comprising individual reproducing head and recording head, is used.

[0006] In this type of head, a MR (Magnetoresistive) head or a GMR (Giant Magnetoresistive) head is used for the reproducing head and an inductive head formed by thin film technology is used for the recording head.

[0007] This type of head has complex structures, fluctuations in quality through the manufacturing process are larger, and recording and reproducing characteristics considerably vary in every magnetic head. To enable the stable recording and reproducing at the desired recording density, only magnetic heads having good characteristic must be assembled. For this purpose, before the magnetic head is assembled in the magnetic disk device, generally the recording and reproducing characteristics of a magnetic head are measured in form of a head suspension assembly (an assembly structure including suspensions which are provided for each recording and reproducing head, and an arm) and good magnetic heads are selected.

[0008] Items to be measured are resistance of the MR head, the physical positions (offset value) of the reproducing head and the recording head, reproducing output voltage, reproducing resolution, over write characteristic, and noise characteristic. At the measurement, it is executed also that recording current of the recording head and bias current of the reproducing head are varied individually and optimum recording current and optimum bias current are obtained.

[0009] Accompanied with increase of the data transfer rate of the magnetic disk device, deterioration of output signal is prevented by cutting down length of a signal transmission line by mounting a head amplifier which amplifies the reproducing signal from the magnetic head and drives the recording head, on the suspension or the arm (called as chip on suspension or chip on arm). In this case, at the selecting measurement in the form of the head suspension assembly, performance is evaluated with output signal of the head amplifier, which shows integrated characteristics of the magnetic head characteristics and the head amplifier characteristics.

SUMMARY OF THE INVENTION

[0010] As described above, at the selecting measurement in the form of the head suspension assembly, the optimization of the control parameters is executed by following measurements: the measurement of the optimum recording current of the recording head, the measurement of the optimum bias current of the reproducing head, the measurement of the offset position of the recording head and the reproducing head, and the measurement of the head amplifier gain and the acceptance or rejection of each magnetic head is decided by setting up the optimum controlling parameter for each magnetic head. But these optimized control parameters obtained are not memorized, and, at shipping inspection of the magnetic disk device, similar optimization is executed again.

[0011] At the shipping inspection of the magnetic disk device, as the optimum recording current and the optimum bias current of each magnetic head are not known, the default value to be sufficient for starting the magnetic disk device is set up. The value to be set up is obtained from sampling the characteristics of plural magnetic disk devices, and is decided to be the value to secure the characteristic not to disturb operation of the magnetic disk drives in the shipping inspection, therefore the default value cannot correspond to the variation of the characteristics of each magnetic head, and it may be occurred that some of the magnetic disk drives are rejected at the shipping inspection of the magnetic disk devices.

[0012] For example, at the shipping inspection of the recording and reproducing characteristic under the condition that the bias current of the reproducing head is set up to the default value but not to the optimum value for each head, it is possible that, if the default value is close to the upper or lower allowable limit of the inspected magnetic head, the inspected magnetic disk device is rejected at the shipping inspection about the recording and reproducing characteristics. Therefore, there has been a problem that the yield is poor in the production of the devices.

[0013] Further, if the head suspension assembly is of said chip on suspension or chip on arm, there is a draw back that the signal level amplified by the head amplifier is merely evaluated at the selection measurement of the magnetic head in the form of the head suspension assembly and the signal level at the output terminals of the magnetic head cannot be measured accurately as the output signal is decided by the integrated characteristics of both magnetic head and head amplifier.

[0014] The present invention mainly uses following structures:

[0015] a head suspension assembly comprising an arm supported so as to rotate, an elastically flexible suspension of which one end is fixed to an end of said arm and the other end mounts the magnetic head, and a signal transmission line which is fixed on said suspension and said arm and connects said magnetic head to a main FPC, wherein a nonvolatile memory which stores the control parameters of said magnetic head is mounted and said nonvolatile memory is electrically connected to said signal transmission line.

[0016] a head suspension assembly comprising an arm supported so as to rotate, an elastically flexible suspension of which one end is fixed to an end of said arm and other end mounts the magnetic head, and a signal transmission line which is fixed on said suspension and said arm and connects said magnetic head to a main FPC, wherein a head amplifier which transmits and receives signals to and from said magnetic head and a nonvolatile memory which stores the control parameter of said magnetic head and said head amplifier, are mounted together, and said head amplifier and said nonvolatile memory are electrically connected to said signal transmission line.

[0017] a magnetic disk device comprising a magnetic disk, a read write circuit, a head suspension assembly which has a magnetic head, an arm supported so as to rotate, an elastically flexible suspension of which one end is fixed to an end of said arm and other end mounts the magnetic head, and a signal transmission line fixed on said suspension and said arm which connects said magnetic head to a main FPC, a storing means which stores control parameters specific to the magnetic disk device and the control parameters corresponding to operating mode of the magnetic disk device, and control means which inspects or controls the magnetic disk device based on control programs and said control parameters stored in said storing means, wherein a nonvolatile memory which stores optimized control parameters depending on a magnetic head at the inspection in the form of said head suspension assembly, is mounted on said head suspension assembly, and, at the inspection of the magnetic disk device, said control means read out the default control parameters stored in said storing means together with the optimized control parameters stored in said nonvolatile memory and execute the inspection.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a figure illustrating the whole structure of a magnetic disk device of the first preferred embodiment of the present invention.

[0019]FIG. 2 is a top view figure of a head suspension assembly provided in the magnetic disk device of the first preferred embodiment of the present invention.

[0020]FIG. 3 is a flow chart showing a method of setting up an operation parameter at shipping inspection of a conventional magnetic disk device.

[0021]FIG. 4 is a flow chart showing a method of setting up an operation parameter in the magnetic disk device of the first preferred embodiment of the present invention.

[0022]FIG. 5 is a figure illustrating the whole structure of a magnetic disk device of the second preferred embodiment of the present invention.

[0023]FIG. 6 is a top view figure of a head suspension assembly provided in the magnetic disk device of the second preferred embodiment of the present invention.

[0024]FIG. 7 is a flow chart showing a method of setting up an operation parameter of the magnetic disk device of the second preferred embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] A head suspension assembly mounting a nonvolatile memory and a magnetic disk device using it, which are the preferred embodiment of the present invention, is disclosed referring to Figures, FIG. 1˜FIG. 7.

[0026] [The First Preferred Embodiment of the Present Invention]

[0027]FIG. 1 is a figure illustrating the whole structure of a magnetic disk device of the first preferred embodiment of the present invention. In FIG. 1, a magnetic disk 1 is a medium for recording or reproducing data, and a magnetic head 2 is a transducer for writing (recording) data to the magnetic disk 1 and reading (reproducing) data from the magnetic disk 1. Generally, a plurality of the magnetic disks 1 are stacked and one magnetic head 2 is placed on each data surface of each magnetic disk respectively.

[0028] A magnetic layer to record data is formed on the surface of the magnetic disk 1, and a lot of data tracks of concentric circles are formed on the magnetic disk surface beforehand, which are divided in radial direction into plural zones, for example, twelve zones of zone 0, zone 1 . . . and zone 11, and each zone comprises plural data tracks. Plural servo areas recording servo data which are necessary for positioning control of a head carriage assembly, are provided in each track. An area between the servo areas is a user area and plural data sectors are formed in the user area. Generally, the user data are recorded in the data sectors. Further, a management data area for storing the management data required for the operation of the drive, is provided in a specified user area. The head suspension assembly has a structure comprising suspensions provided for each magnetic head and an arm, and the head carriage assembly has a structure comprising a group of the suspensions provided for each magnetic head corresponding to every magnetic disk in the stacked disks and a group of the arms.

[0029] The magnetic disk 1 is rotated at high speed by a spindle motor 3. The head carriage assembly mounts the magnetic heads 2 at its front edge, is swung by a voice coil motor 5, and moves the magnetic heads 2 to any target position on the magnetic disk. The spindle motor 3 and the voice coil motor 5 are connected electrically to a spindle/VCM drive circuit 6. The spindle/VCM drive circuit 6 drives the voice coil motor by giving the control current to the voice coil motor 5, and also drives the spindle motor 3 by giving control current to the spindle motor 3. The spindle/VCM drive circuit 6 is controlled by MPU 7.

[0030] Each magnetic head 2 is electrically connected to a head amplifier 8 through a main flexible printed circuit board (FPC) 20 and a flexible printed circuit board (FPC) 18 fixed on a suspension 16 and an arm 17 which comprise the head suspension assembly 4. The head amplifier 8 amplifies reproducing signal read by the reproducing head of the magnetic head 2, and drives the recording head of the magnetic head 2 by converting digital write signal data from a read/write circuit into analog signal wave form. This head amplifier 8 also writes and read data to and from the nonvolatile rewritable memory that is described below.

[0031] Read/write circuit 11 has a decoding function that decodes analog input signal transmitted from a head amplifier 8 to original data, which is necessary for data reproducing operation. For example, this decoding function is realized by the PRML (Partial Response Maximum Likelihood) reproducing circuit. This reproducing circuit has a well-known circuit structure comprising an auto gain control amplifier, a low pass filter, an analog-to-digital converter, an equalizer, Viterbi detector, and PLL circuit (these circuits are not shown).

[0032] The read/write circuit 11, in addition to above decoding function, has an encoding function which is a signal processing function required for recording data to the magnetic disk, and a reproducing function of the servo data required for the servo control process such as a head positioning control.

[0033] MPU 7 controls every function of the magnetic disk device according to a control program and a control parameters stored in Flash ROM (FROM), which is described later. Namely, it executes well-known controls such as the positioning control to move the magnetic head 2 to a target position on the magnetic disk 1, and a control of transferring recording and reproducing data by controlling HDC (Hard Disk Drive Controller) 12.

[0034] In a initializing process after turning on of power of the magnetic disk device, MPU 7 controls transferring management data, namely various control parameters specific to each device and operating mode, which are stored in FROM, to a RAM 14, and also controls storing the management data in FROM 15 corresponding to FROM set command from a host PC through a host interface.

[0035] MPU 7 is connected to a nonvolatile rewritable FROM 15 which stores control programs (firmware) for controlling every function of the magnetic disk device, and a rewritable volatile RAM 14 used for a work memory area of MPU 7 and a storing area of the control parameters and the operating mode that MPU 7 uses in the operation of the magnetic disk device.

[0036] HDC 12 controls communications of commands and data with the host PC through the host interface. HDC 12 also controls the data communication with the read/write circuit.

[0037] As the control parameters used in the control programs of the magnetic disk device, there are the control parameters specific to the device not depending on each of the magnetic heads, the control parameters concerning the operating mode of the device and the parameters depending on each of the magnetic heads.

[0038] As the parameters specific to the device not depending on the magnetic head, there are the serial numbers of the device, the revision number of the firmware, defect address data that records positions of defects on the magnetic disks. As the parameters concerning the operating mode of the device, there are waiting time in which rotation of spindle reaches the normal speed after turning on the power, the operating mode whether the spindle is spun up or not just after the turning on power (Power On spin up mode), master/slave operating mode, and ON/OFF of a cache memory. As the control parameters depending on each magnetic head, there are a recording current of the magnetic head, a bias current of the reproducing head, a resistance of the reproducing head, the offset value of the recording head and reproducing head, an amount of overshoot of the rerecording current waveform, an amount of write pre-compensation, a cutoff frequency of a low pass filter (LPF), and an amount of a boost of LPF. These control parameters depending on each magnetic head can be set up to optimum value corresponding to characteristics of each zone formed on the magnetic disk.

[0039] The nonvolatile memory 9 is a rewritable EEPROM and stores merely the parameters depending on each of the magnetic heads among the above-described control parameters. In the selecting measurement of the magnetic heads in form of the head suspension assembly, operating parameters optimized with an adjustment are recorded by MPU of a selection tester. After the magnetic heads are assembled into the magnetic disk device, at the shipment inspection of the magnetic disk device, MPU 7 reads out the control parameters through the head amplifier, the read/write circuit, and HDC.

[0040]FIG. 2 is the top view figure of the head suspension assembly showing a mounting method of the nonvolatile rewritable memory 9. The magnetic head 2 is mounted at the front edge of a suspension 16 and electrically connected to a connecting terminal 19 with FPC 18 a and FPC 18 b. A main FPC 20 connects the connecting terminal 19 to a head amplifier 8. The optimized control parameter depending on the magnetic head is stored in said nonvolatile memory 9 as described above.

[0041] The nonvolatile memory 9 is connected to the connecting terminal 19 with FPC 18 a, and to the head amplifier 8 with the main FPC 20.

[0042] The method of setting the control parameters for the magnetic disk device which has the structure shown in FIG. 1, is described referring to the flow charts shown in FIG. 3 and FIG. 4, for example, in case of the shipping inspection of the magnetic disk device of the present invention. FIG. 3 shows setting process of the control parameters at the inspection of the conventional magnetic disk device having no rewritable nonvolatile memory on the head suspension assembly.

[0043] When the power of the magnetic disk device is turned on, default control parameters (three kinds of control parameters described above, which are specific to the device, concerning the operating mode, and depending on each magnetic head respectively) are read from the data area of FROM 15 by MPU according to the initializing routine of the control program stored in FROM 15 which is placed on a circuit board outside the head suspension assembly (step 100). The control parameters read out and the control programs to control the drive are developed or transferred in RAM 14 (step 101), and the rotating operation of the spindle and the seek operation of the magnetic head are executed using the default control parameters transferred in RAM 14 (step 102). Then, the control parameters are adjusted (step 103), and the adjusted and optimized control parameters are recorded in the management area on the magnetic disk (step 104).

[0044]FIG. 4 is a flowchart showing the process of setting control parameters at the inspection of the magnetic disk device of the preferred embodiment of the present invention. In this flowchart, the difference from the conventional case shown in FIG. 3 is that this processing method includes the step of reading out the control parameters depending on each of the magnetic heads at a step 201 from a nonvolatile EEPROM placed on the head suspension assembly. The control parameters read out at this step is not the default value that is the average value for the magnetic heads, but the optimized values having been set for each of the magnetic heads at the selecting test in form of the head suspension assembly.

[0045] A problem in the conventional case shown in FIG. 3 is that the magnetic disk device is operated using the default values not optimized for each of the magnetic heads and the head amplifiers at the step 102, and sometimes the magnetic disk devices do not operate or fall into unstable operation.

[0046] As this preferred embodiment of the present invention, by mounting a rewritable nonvolatile memory on the head suspension assembly and storing the optimized control parameters depending on each of magnetic heads, which are optimized in form of the head suspension assembly, the instability of the operation of the magnetic disk devices at the inspection can be avoided and the yield of the magnetic disk devices can be improved.

[0047] More specifically, for example, regarding to the bias current of the reproducing head, which is one of the control parameters, the optimum bias current is set up at the selecting test in form of the head suspension assembly having said reproducing head, and the set value is stored in the nonvolatile memory on said head suspension assembly. At the inspection of the magnetic disk device, the optimized control parameters depending on each of the magnetic heads as the bias current of the reproducing head (the control parameters other than the bias current, which depend on each of the magnetic head, have been stored also in the nonvolatile memory) are read out from the nonvolatile memory and transferred in RAM 14 (step 202), and further, the control parameters specific to the magnetic disk device and the control parameters concerning the operating mode are read from FROM and transferred in RAM (“default control parameters” in the step 202 means both control parameters read from FROM and optimized control parameters read from EEPROM).

[0048] Subsequently, the device shipping inspection is executed by operating the magnetic disk device actually using all the control parameters transferred in RAM from said FROM and EEPROM, all the control parameters are adjusted so as to optimize the operation of the magnetic disk devices (step 204), and the adjusted optimized control parameters are recorded in the management data area on the magnetic disk (step 205). At step 204, when, among the all optimized parameters, the value of the control parameter that depends on the magnetic head, is varied from the value stored in EEPROM, the control parameters varied and adjusted can be restored by rewriting. Then, the rewritten values of the control parameters can be utilized effectively in case that the head carriage assembly which is an assembly of the head suspension assemblies is removed and reinstalled into the other same type magnetic disk device.

[0049] [Second Preferred Embodiment of the Present Invention]

[0050]FIG. 5 is a figure illustrating the whole structure of a magnetic disk device of the second preferred embodiment of the present invention. In FIG. 5, magnetic disk 1, magnetic head 2, spindle motor 3, voice coil motor 5, spindle/VCM drive circuit 6, MPU 7, read write circuit 11, HDC 12, host interface 13, RAM 14, FROM 15, connecting terminal 19 and main FPC 20 have the similar structure, function and operation with those of the first embodiment of the present invention shown in FIG. 1, and then, the description of these composing elements in FIG. 1 can be applied.

[0051] Each magnetic head 2 is electrically connected to a head amplifier 8 with a flexible printed circuit board (FPC) 18 that is fixed on a suspension 16 and an arm 17, which comprise a head suspension assembly 4. The head amplifier 8 amplifies the reproducing signal from the reproducing head of the magnetic head 2, converts the digital write signal from the read/write circuit to the analog signal waveform, and drives the recording head of the magnetic head 2.

[0052] A head amplifier controller 10 switches the head amplifiers 8 provided in each head suspension assembly, transmits the recording data output from the read/write circuit 11 to each head amplifier 8, receives an amplified reproducing signal from each head amplifier 8, and transmits the amplified reproducing signal to the read/write circuit 11. The head amplifier in FIG. 1 has both functions above described of the head amplifier 8 and the head amplifier controller 10.

[0053] In the second preferred embodiment of the present invention, the head suspension assembly 4 mounts the head amplifier 8 in addition to the nonvolatile EEPROM 9, and the head amplifier and the nonvolatile memory are electrically connected with FPC 18 which is fixed on the suspension and the arm. The outline of electric connection is that one of the terminals of the head amplifier 8 is connected to the input output terminal of the magnetic head 2, the other terminal of the head amplifier 8 is connected to the connecting terminal 19 (connecting point with the main FPC 20) of FPC 18, and EEPROM 9 is connected to the connecting terminal 19 and the third terminal of the head amplifier 8 (for example, a terminal for controlling the amplifier gain).

[0054] As the control parameters used in the control programs of the magnetic disk device, there are the control parameters specific to the device not depending on each magnetic head or the head amplifier, the control parameters concerning the operating mode of the device, and the parameters depending on each of the magnetic heads and the head amplifiers. As the parameters specific to the device not depending on the magnetic head or the head amplifier, there are the serial numbers of the device, the revision number of the firmware, defect address data that records positions of defects on the magnetic disks. As the parameters concerning the operating mode of the device, there are waiting time in which rotation of spindle reaches the normal speed after turning on the power, operating mode whether the spindle is spin up or not just after the turning on power (Power On spin up mode), master/slave operating mode, and ON/OFF of a cache memory. As the control parameters depending on each magnetic head or head amplifier, there are a recording current of the magnetic head, a bias current of the reproducing head, a resistance of the reproducing head, the offset value of the recording head and reproducing head, gain of the head amplifier, an amount of overshoot of the rerecording current waveform, an amount of write pre-compensation, cutoff frequency of a low pass filter (LPF), and an amount of the boost of LPF. These control parameters depending on each magnetic head or head amplifier can be set to optimum value corresponding to characteristics of each zone formed on the magnetic disk.

[0055] The nonvolatile memory 9 is rewritable EEPROM and stores merely the parameters depending on each magnetic head or head amplifier among the above-described control parameters.

[0056] In the selecting measurement of the magnetic heads in the form of the head suspension assembly, the adjusted and optimized control parameters are recorded in a nonvolatile memory by MPU in a selection tester. After the magnetic heads are assembled into the magnetic disk device, at the shipment inspection of the magnetic disk device, MPU 7 reads out the control parameters in the nonvolatile memory through the head amplifier controller 10, the read/write circuit 11, and HDC 12.

[0057]FIG. 6 is the top view figure of the head suspension assembly showing a mounting method of the nonvolatile memory 9. The magnetic head 2 is mounted at the front edge of the suspension 16 and electrically connected to the head amplifier 8 with FPC 18 b. The head amplifier 8 is also electrically connected to FPC 18 c, and FPC 18 c is connected to the connecting terminal 19. The connecting terminal 19 is connected to the head amplifier controller 10 through a main FPC 20. The optimized control parameters depending on the magnetic head as described above are stored in the nonvolatile memory 9. The nonvolatile memory 9 is connected to the connecting terminal 19 through FPC 18 a, and, further, to the head amplifier controller 10 through the main FPC 20.

[0058] The method of setting the control parameters for the magnetic disk device having the structure shown in FIG. 5 is described referring to the flow charts of FIG. 3 and FIG. 7, for example, in case of the shipping inspection of the magnetic disk device of the present invention. FIG. 3 shows setting process of the control parameters at the inspection of the conventional magnetic disk device having no rewritable nonvolatile memory on the head suspension assembly, and this method are explained already at the description of the first preferred embodiment of the present invention.

[0059]FIG. 7 shows the setting process of the control parameters at the inspection of the magnetic disk device of the second preferred embodiment of the present invention. In FIG. 7, the difference from the conventional case shown in FIG. 3 is that this processing method includes the step of reading out the control parameters depending on each of the magnetic heads and the head amplifiers at a step 301 from a nonvolatile EEPROM placed on the head suspension assembly. The control parameters read out at this step is the optimized values having been set up for each of the magnetic heads previously at the selecting test in the form of the head suspension assembly.

[0060] The problems in the conventional case shown in FIG. 3 are that the magnetic disk device is operated using the default values not optimized for each of the magnetic heads and the head amplifier at the step 102, and sometimes the magnetic disk devices do not operate or fall into unstable operation.

[0061] As this preferred embodiment of the present invention, by mounting a rewritable nonvolatile memory on the head suspension assembly and storing in it the optimized control parameters depending on every magnetic head and the head amplifier, which are optimized in form of the head suspension assembly, the instability of the operation of the magnetic disk devices at the inspection can be avoided and the yield of the magnetic disk devices can be improved.

[0062] Further, in the head suspension assembly of this preferred embodiment of the present invention, the amplification gain of the head amplifier can be measured and stored previously in the nonvolatile memory before the selecting measurement in form of the head suspension assembly and can be used at the selecting measurement. Hereby, the signal levels of the magnetic heads in the selection in form of the head suspension assembly can be measured accurately, and mis-passing of the defective products are prevented and the yield of the magnetic disk devices can be improved.

[0063] Explanation for an actual example is given as follow: the optimized control parameters concerning the magnetic heads such as the bias current of the reproducing head, etc. are obtained at the selecting test in form of the head suspension assembly shown in FIG. 6 and stored in EEPROM 9, and the optimum values of the control parameters concerning the head amplifier 8 such as the amplifier gain, the amount of the overshoot of recording current are obtained previously by testing of single head amplifier before the selecting test in form of the head suspension assembly, and these obtained values are stored in EEPROM 9. Through the procedure similar to step 202 to step 205, all of the control parameters are adjusted, the optimized control parameters after the adjustment are recorded in the management data area on the magnetic disk, or the adjusted control parameters of the magnetic heads and the head amplifiers are rewritten in EEPROM 9.

[0064] Thus, if the shipping inspection of the magnetic disk device including the test of the recording and reproducing characteristics is executed using the optimized values concerning the magnetic head and the head amplifier, which are optimized at the test in state of the head suspension assembly, the rejection rate is reduced in comparison with it of the conventional case shown in FIG. 3 where the shipping inspection of the recording and reproducing characteristics is executed using the average default values for the magnetic head and the head amplifier (in case the default values are close to the upper or lower allowable limit of the magnetic heads to be inspected, there is a possibility of rejection of the magnetic disk device at the shipping test of the recording and reproducing characteristics). When the head suspension assembly is a chip on suspension type or a chip on arm type, at the selecting measurement of the magnetic heads in form of head suspension assembly, the control parameters of the magnetic heads and the head amplifiers are optimized independently and stored respectively in the nonvolatile memory 9, the shipping inspection of the magnetic disk device is executed using these optimum value, the signal level at the reproducing output terminal of the magnetic head can be measured accurately because the control parameters of the head amplifier is given previously, and the adjustment of the control parameters of the magnetic head can be executed (step 304).

[0065] In this preferred embodiment of the present invention, a configuration example is disclosed, in which the separate packages of the head amplifier 8 and the rewritable nonvolatile memory 9 are placed on the head suspension assembly 4 as shown in FIG. 5 and FIG. 6, but the present invention is not limited to these preferred embodiments, but various modifications are possible within the scope of this invention. For example, it is possible that both the head amplifier 8 and the rewritable nonvolatile memory 9 are accommodated in one package. By employing this configuration, the amplification gain of the head amplifier can be measured in form of a chip and can be stored in the rewritable nonvolatile memory, the testing steps can be decreased, and the manufacturing cost can be reduced by reduction of number of components.

[0066] As described above, according to the magnetic disk device and the head suspension assembly of the first and the second preferred embodiments of the present invention, a data storage is provided on the head suspension assembly, therefore the optimized control parameters of each of the head suspension assemblies can be stored in the data storage at the selecting measurement of the head suspension assembly, and the stored optimized control parameters can be utilized in the shipping inspection of the magnetic disk devices. Therefore, as the control parameters optimized for each head suspension assembly can be used, the magnetic disk device can be inspected at satisfactory state regardless of the variations of the characteristics of the magnetic head and the head amplifier, and the yield of the devices can be improved.

[0067] According to the present invention, by providing the rewritable nonvolatile memory on the head suspension assembly and storing the optimized control parameters of the magnetic heads and/or the head amplifier in this memory, the yield of the magnetic disk device using this head suspension assembly at the shipping inspection can be improved.

[0068] According to the present invention, by measuring the amplifier gain of the head amplifier in advance and storing it in the rewritable nonvolatile memory, the head output signal level can be measured directly and accurately at the selecting measurement in form of the head suspension assembly. 

What is claimed is:
 1. A head suspension assembly comprising; an arm which is supported so as to rotate, a suspension which one end is fixed to an end of said arm and the other end mounts a magnetic head, a signal transmission line which connects said magnetic head to a circuit board electrically, and a nonvolatile memory which stores control parameters of said magnetic head.
 2. The head suspension assembly according to claim 1 ; wherein said control parameters comprise at least one of the following: a recording current, a bias current in reproducing data from a magnetic disk, resistance of a reproducing head, offset value of a recording head position and a reproducing head position, an overshoot amount of a recording current waveform, an amount of write pre-compensation, a cutoff frequency of a low pass filter (LPF), and an amount of a boost of LPF.
 3. A magnetic disk device using the head suspension assembly according to claim 1 .
 4. A head suspension assembly comprising; an arm which is supported so as to rotate, a suspension which one end is fixed to an end of said arm and the other end mounts a magnetic head, a head amplifier which transmits and receives signals to and from said magnetic head, a signal transmission line which connects said magnetic head to a circuit board electrically, and a nonvolatile memory which stores control parameters of said magnetic head and said head amplifier.
 5. A head suspension assembly according to claim 4 , wherein said control parameters comprise at least one of the following: a recording current, a bias current in reproducing data from a magnetic disk, resistance of a reproducing head, offset value of a recording head position and a reproducing head position, an overshoot amount of a recording current waveform, an amount of write pre-compensation, a cutoff frequency of a low pass filter (LPF), and an amount of a boost of LPF.
 6. A magnetic disk device using the head suspension assembly according to claim 4 .
 7. A magnetic disk device comprising; a magnetic disk which records data, a read/write circuit which has a decoding function for data reproducing operation, a head suspension assembly which has a magnetic head, an arm which is supported so as to rotate, a suspension which one end is fixed to an end of said arm and the other end mounts a magnetic head, and a signal transmission line which is fixed on said suspension and said arm and connects said magnetic head to a main FPC electrically, a nonvolatile memory which is mounted on said head suspension assembly and, at the inspection in form of said head suspension assembly, stores optimized control parameters depending on said magnetic head, a memory which stores control parameters specific to a magnetic disk device and control parameters concerning the operating mode of a magnetic disk device, and a control means which controls and inspects a magnetic disk device based on control programs and said control parameters stored in said storage, wherein said control means operates and inspects said magnetic disk device based on said optimized control parameters read from said nonvolatile memory and default control parameters read from said memory at inspection of magnetic disk device.
 8. A magnetic disk device according to claim 7 , wherein said head suspension assembly mounts a head amplifier which transmits and receives signals to and from said magnetic head, and said nonvolatile memory stores optimized control parameters of said head amplifier in addition to said optimized control parameters of said magnetic head. 